Hitherto, it has been very difficult to record data (e.g., date on which a photograph is taken, weather, magnification, the number of prints) onto a silver halide photographic material (hereinafter, photographic material) while photographing with a camera. The date on which a photographic was taken could be optically recorded on the light-sensitive emulsion layer of the photographic material. It was very difficult to record onto the photographic material itself during printing. This is a severe disadvantage in a high-speed operation and results in a loss of efficiency.
The recording of various information onto a photographic material is a very important means for enhancement of camera operability and simplification. The use of magnetic recording system as a means for recording information has been studied, because input and output is arbitrarily made, and the system is inexpensive. For example, U.S. Pat. Nos. 3,782,947, 4,279,945 and 4,302,523 disclose a magnetic recording layer is provided on the back side of a photographic material having a transparent support, the magnetic recording layer is provided with the requisite degee of transparency for the photographic materials during photographing with no adverse effection graininess by appropriately selecting the amount of magnetic particles to be contained in the magnetic recording layer. Systems for recording signals onto the magnetic recording layer are disclosed in WO 90-4205 and WO 90-04212.
The recording of various information onto the photographic material (which was conventionally difficult), is made possible by providing magnetic recording layer and an input and output system (e.g., recording and reproduction system). For example, it is now possible to record onto the magnetic layer of the photographic material the date of photographing, weather and illumination conditions, photographing conditions such as reduction/enlargement rate, etc., the number of re-prints, places to be zoomed, development of messages, etc. and printing conditions, and to later read the recording information. Furthermore, it is expected that the reproduced information from the photographic material can constitute output signal means to directly form, e.g., TV/video image.
Photographic materials having a transparent magnetic recording layer are disclosed in JP-B-57-6576 (the term "JP-B" as used herein means an "examined Japanese patent publication") and JP-A-53-109604 (thee term "JP-A" as used herein means as "unexamined published Japanese patent application"). Magnetic recording layers containing .gamma.-iron (III) oxide as proposed in these patent specifications have a low transmittance to light in the visible region. Hence, it has been desired to provide a magnetic recording layer having a higher transmittance for use in a photographic material.
Further more, magnetic recording layers containing .gamma.-iron (III) oxide have a low transmittance to light having short wavelengths and high transmittance to light of long wavelengths. Accordingly, optical density of the magnetic recording layer is highly dependent on the wavelength of the light which is photographically undesirable. It has been a need to develop a magnetic recording layer having a constant optical density as a function of incident wavelength, namely, a magnetic recording layer having a transparency near neutral gray.